The invention relates generally to gas appliances, and more particularly to ignition devices for igniting a flow of gas in gas appliances and other gas-fired equipment. The invention may be applied to any application where ignition of a fuel air mixture is required.
Conventional gas appliances, such as those found in households, have one or more burners in which gas is mixed with air and burned at a cooktop or in an enclosed space, such as an oven. Various types of igniters are employed in such gas appliances for igniting the flow of gas. For example, in some systems spark igniters are employed that generate a spark to ignite the gas flowing to the burner. In certain other systems, ceramic hot surface igniters are employed that include heating elements for generating sufficient heat to ignite the gas supplied to the burner.
In certain systems, silicon carbide or silicon nitride hot surface igniters are employed for igniting the gas flow. Some of the problems with these conventional igniters are that they are porous, fragile, power hungry, relatively expensive and are fairly slow to reach ignition temperature. In addition, the resistance versus temperature characteristics of these conventional silicon carbide igniters may alter or drift over time, thereby adversely affecting their reliability.
Unfortunately, existing hot surface igniters need substantially high power for operation and can require an unacceptably long time to reach the required temperature for ignition. Further, heating elements of the igniters are exposed to the environment, resulting in accelerated failure of such elements due to degradation and contamination of the elements. Additionally, such igniters are often subjected to impacts from an operator during routine cleaning and maintenance, which may cause the igniter to break. Furthermore, such igniters require precise control of the voltage supplied to the heating elements. For example, a relatively high voltage may result in premature failure of the heating elements. Similarly, an applied voltage less than the required voltage may result in poor performance of the igniter.
Accordingly, it would be desirable to develop an ignition device for a gas appliance that has reduced power and voltage requirements. It would also be advantageous to develop an ignition device that requires relatively less time to reach the required ignition temperature, and is more robust and reliable.